Typical symptoms experienced by those suffering from an upper respiratory tract infection such as the common cold or flu can include nasal congestion, runny nose, sneezing, headache, dry cough, sore throat, sinus pressure or pain, chest congestion, muscle aches/pains, wet/chesty cough, fever, and combinations thereof. As a result, many multiple symptom relief (MSR) products have been developed to treat a variety of these symptoms simultaneously.
For optimal efficacy, many MSR products must be taken every four to six hours. However, it would be desirable for an MSR product to deliver symptom relief over a longer period of time. An extended relief product can be more convenient for consumers and can improve dosing compliance, which can ultimately enhance the overall effectiveness of the product.
One problem with developing an extended relief MSR product is that each active has a different duration of action and pharmacokinetic behavior in the human body. For instance, the half-life of immediate release naproxen sodium (NAP) is 12-24 hours, the half-life of immediate release pseudoephedrine hydrochloride (PSE) is 4.3-8 hours, and the half-life of immediate release dextromethorphan hydrobromide (DXM) is 3-5 hours. Matching the duration of action for each active over an extended time period, for instance 8 or 12 hours, within a single dosage form requires modification of the release characteristics for each active and significant tailoring of the dose form through the use of immediate, extended, delayed or mixed release formulation technologies. Furthermore, when NAP, PSE and DXM are combined in one dosage form, the PK profile of the immediate release NAP and the extended release PSE and DXM can be different than if the actives are used alone or in combination with just one other active due to interactions between excipients and/or actives.
In addition, it is difficult to formulate a stable MSR product because some actives can undergo an oxidation reaction due to the interaction with excipients and certain processing conditions, resulting in the formation of unwanted degradation products.
As such, there remains a need in the area of over-the-counter (OTC) drugs for improved options for the treatment of symptoms associated with the common cold, influenza, or respiratory allergies. In particular, there is a need for a stable, convenient and highly effective MSR product that comprises a pain reliever, a decongestant, and an antitussive in a dosage form that provides relief over an extended period of time.